1. Technical Field
The present invention relates to an image forming apparatus utilizing e.g. an electrophotographic technology, and a cleaning device.
2. Related Art
In an electrophotographic image forming apparatus such as a copier or a printer, a photoreceptor having e.g. a drum shape (photoreceptor drum) is uniformly charged with a charging device to a predetermined potential, and is exposed to light controlled based on image information, thereby an electrostatic latent image is formed. Then the electrostatic latent image is developed with a developing unit to a toner image, then transferred and fixed onto a recording sheet.
Further, after the transfer in this image formation process, a little amount of residual toner which has not been transferred exists on the surface of the photoreceptor drum. To eliminate the residual toner on the surface of the photoreceptor drum before the photoreceptor drum is charged again, a cleaning device is provided on the downstream side of the transfer unit.
The diameter of the toner particle on the photoreceptor drum after the transfer is several μm to several tens of μm. In the cleaning device, to eliminate the toner particles, a structure having a roller type cleaning member, rotated with a peripheral velocity difference from the photoreceptor drum, in contact with the surface of the photoreceptor drum, or a structure having a blade type cleaning member in edge-contact with the surface of the photoreceptor drum, is generally used.
Further, when the charging device charges the photoreceptor drum, corona effluence such as nitrogen oxides (NOx) is generated by discharge, and attached to the surface of the photoreceptor drum. The corona effluence is much finer than toner particles, and has a characteristic of absorbing moisture and reducing resistance. When the cleaning device is arranged only to eliminate residual toner, the corona effluence attached to the surface of the photoreceptor drum cannot be sufficiently eliminated. Then, the corona effluence which have not been eliminated and remained on the surface of the photoreceptor drum may cause so-called “image deletion” meaning white spot in an image in a high temperature and humidity environment. Accordingly, in some machines where a considerable amount of corona effluence is generated such as a high speed image forming apparatuses and color image forming apparatuses, the cleaning device is arranged so as to eliminate corona effluence in addition to toner particles.